Until fairly recently, the cable network was predominantly a vehicle for delivering entertainment. With the advent of the Internet and the rise in demand for broadband two-way access, the cable industry began to seek new ways of utilizing its existing plant. Pure coaxial (“coax”) cable networks were replaced with hybrid fiber networks (HFNs) using optical fiber from the head end to the demarcation with the subscriber coax (usually at a fiber node). Currently, a content-based network, a non-limiting example of which is a cable television network, may afford access to a variety of services besides television, for example, broadband Internet access, telephone service, and the like.
One significant issue for a cable operator desiring to provide digital service is the configuration of its network. Designed for one-way delivery of broadcast signals, the existing cable network topology was optimized for downstream only (i.e., towards the subscriber) service. New equipment had to be added to the network to provide two-way communication. To reduce the cost of this equipment and to simplify the upgrade of the broadcast cable for two-way digital traffic, standards were developed for a variety of new cable-based services. The first of these standards, the Data Over Cable System Interface Standard (DOCSIS® standard), was released in 1998. DOCSIS® establishes standards for cable modems and supporting equipment. DOCSIS® (Data Over Cable Service Interface Specification) is a registered mark of Cable Television Laboratories, Inc., 400 Centennial Parkway Louisville Colo. 80027, USA, and will be referred to for the remainder of this application in capital letters, without the ® symbol, for convenience.
There are many types of IP networks besides cable networks. Other wired IP networks include, for example, digital subscriber line (DSL), fiber to the home, fiber to the curb, and so on. Wireless IP networks include Wi-Fi, wireless ISP (Internet Service Provider), WiMAX, satellite internet, and mobile broadband.
In contrast to traditional television service, Internet Protocol television (IPTV) is a system through which television services are delivered using the Internet protocol suite over a packet-switched network such as a LAN or the Internet, instead of being delivered through traditional terrestrial, satellite signal, and cable television formats. IPTV can be delivered over any IP network, including but not limited to a cable network. In most cases, IPTV over a cable network will utilize QAMs dedicated to data transport as distinguished from QAMs allocated for traditional video content delivery (QAM=Quadrature amplitude modulation). IPTV can be consumed at many different devices; one non-limiting example is a gaming console such as the Microsoft Xbox® video game console (registered mark of Microsoft Corporation, Redmond Wash., USA).